package acm.蓝桥13;

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        long a = sc.nextLong();
        long b=sc.nextLong();
        long c=sc.nextLong();
        long ab=a*5+b*2;
        long week=c/ab*7;
        long mod=c%ab;
        long cur=0;
        long i=0;
        while (cur<mod&&i<5){
            i++;
            cur+=a;
        }
        if (cur>=mod){
            System.out.println(week+i);
            return;
        }
        while (cur<mod&&i<7){
            i++;
            cur+=b;
        }
        System.out.println(week+i);
    }
}
